influence of the atmospheric precipitation phase composition on seasonal evolution of snow-ice cover in the taganrog bay apex

Purpose. The present study is aimed at assessing influence of the atmospheric precipitation phase composition upon simulation of seasonal evolution of ice thickness in the Taganrog Bay apex. Methods and Results. The ice regime characteristics in the northeastern part of the Taganrog Bay were studied by means of the ice cover thermodynamic model. The observational data on the basic meteorological parameters obtained every 3 hours per day at the meteorological station Taganrog were used as a meteorological forcing. The simulations included the static and dynamic methods for dividing total prognostic precipitation into the liquid and solid fractions. The first method implied presence of the temperature threshold, below which all the precipitations were classified as snow and above which – as rain. The second one took into account gradual transition from rain to snow within the preset temperature interval. For the winters differing in precipitation amount during the ice period, the comparative analysis of the results of simulating the sea ice thickness seasonal evolution was done, and the model sensitivity to choosing the method for determining the portions of the solid and liquid phases was assessed. Simulation veracity was defined through comparison of the sea ice thickness model values with the actual ones from the USIWO ice maps for the winter seasons 2007/2008–2010/2011. Conclusions. It is shown that the results obtained by application of the S-like dependence of a snow portion in the atmospheric precipitation within the temperature transition interval, proved to be the most justified from the viewpoint of the root-mean-square deviation and correlation coefficient optimal values. The minimal errors in reproducing the ice thickness seasonal evolution are obtained at the temperature threshold close to 2 °C and the width of the temperature transition interval 5–9 °С. The best results for the low-snow winters are obtained due to applying the static method for determining a precipitation phase.